Please be patient as we perform maintenance

Please be patient as we perform some upgrades to enhance your experience here on For example, we’re producing more video content on our YouTube channel, better organizing our current content, and adding fresh new content that goes beyond developing apps for iOS and macOS. For example, we’ll be looking at the financial performance of Apple’s stock and the stock of related companies, all while sticking to our original purpose of helping developers improve their skills and learn about cutting-edge technologies. Check back soon!

The real importance of WWDC 2021: raw computing power (CPU), raw graphics power (GPU), and big high resolution screens

Photographers can’t professionally fine-tune an image of a mountainous landscape’s foreground and background on a tiny little iPhone screen. A data scientist can’t layout graphs, matrices, vectors, and spreadsheets on a tiny little iPhone screen. A customer service representative can’t troubleshoot a technology problem without searching through several device schematics, handle several different calls at once, be on the phone with one customer, be texting with another customer, and looking at a user’s guide that shows which buttons and switches do what things on a tiny little phone screen. Can you imagine trying to design, read, write, and debug code, and layout your UI with Xcode on an iPhone? (I could on a large iPad or MacBook, but not a phone).

Continue reading “The real importance of WWDC 2021: raw computing power (CPU), raw graphics power (GPU), and big high resolution screens”

We’re still here…

Some of you have been kind enough to ask why we haven’t been publishing for a few months. Thank you for your concern.

We’ve been busy, but be patient as you’ll soon be seeing us post articles again…

And we’ve got some big plans for the future, including books, online courses, and video tutorials, just to name a few.

Stay tuned. Thanks!

Fix for prohibitory symbol (do not enter, stop sign) when booting into or updating macOS Mojave 10.14 (including betas)

FLASH: Updated 11/9/22 with a tutorial on how to obtain installers for macOS Ventura 13.0 and many older macOS versions.
FLASH: Updated 10/25/18 with NEW INSIGHTS on how to deal with the prohibitory symbol. When installing the macOS Mojave 10.14 beta 11 and then the public macOS Mojave 10.14, I ran into the prohibitory symbol again, actually twice during both installations, but got through to the final install in both cases. You should read this entire article, but if you’re in a hurry, jump to the section covering working around hitting the prohibitory symbol twice.

  • If you get the prohibitory symbol multiple times, you may have to shut down and restart your Mac multiple times.
  • Boot into another APFS-based partition, like High Sierra (macOS 10.13), run Disk Utility, and then run First Aid on the Mojave partition. If Disk Utility reports that it fixed the Mojave partition — or even if it just gave the partition a clean bill of health — I’ll bet your problems will be solved.

Continue reading “Fix for prohibitory symbol (do not enter, stop sign) when booting into or updating macOS Mojave 10.14 (including betas)”

Controlling chaos: Why you should care about adding error checking to your iOS apps

NOTE: The second installment of this article, “Controlling chaos: Error Handling in Swift 4 with do, try, catch, defer, throw, throws, Error, and NSError,”, has just been released.

In this tutorial, the first in a series of tutorials, we’re going to discuss the arduous topic of looking for unexpected values, events, and conditions that arise during program execution, using a technique I like to call “error checking.” Today, I’ll concentrate on the reasons why you should check for errors. I’ll mention a number of techniques I use but leave detailed discussion of those techniques and sample code to subsequent articles. The purpose of this tutorial is to convince you to make use of error checking in your apps. You ignore errors at your own dire peril. This is sink or swim. If you put out a crappy app, no one’s going to use it because you’ll get a bad reputation at Internet speed, and employers/customers will be more than happy to leave you behind forever for other app developers who aren’t too lazy to write quality code.

Continue reading “Controlling chaos: Why you should care about adding error checking to your iOS apps”

Downloading and installing an old version of OS X (mac OS) on your Mac

We’re going to talk about installing a version of your Mac’s operating system (OS), known as “macOS” or “OS X,” on your Mac, older than the one you’re currently running, on a partition of your primary hard drive or on an external hard drive. You may find that your current instance of OS X is too unstable for normal day-to-day usage or more heavy-duty tasks like development. Remember all the problems people had when they upgraded to OS X 10.13, also known as “High Sierra?” Oy, vey. You might have been like “Get me the heck outta Dodge!” You wanted or needed to get back to a stable OS, like Sierra (OS X 10.12) or El Capitan (OS X 10.11). For developers, you may have to install an older version of Xcode not supported by your latest OS. For Cocoa/macOS developers, you may need to make absolutely sure that your desktop apps are backward compatible, and the only way to do that for sure is to install and run your apps on older versions of macOS. I will show you, step by step, how to get a valid copy of an older version of macOS, make a bootable installer disk, and install the old OS.

Continue reading “Downloading and installing an old version of OS X (mac OS) on your Mac”

Welcome to iOS Brain

Stayed tuned as we get our infrastructure together. We’ll be publishing information, tutorials, news, tips, workarounds, reviews, etc., of all things iOS. Look for articles on developing iOS apps using Xcode, Interface Builder, Objective-C, Swift, Adaptive Layout, Auto Layout, and more. Related technologies like Git, BitBucket, GitHub, Photoshop, and Sketch will also be covered.

Don’t be surprised if we go off on tangents into subjects like object-oriented programming, debugging, Agile, Test-Driven Development, Continuous Integration, and more.

Thanks for checking in!

Continue reading “Welcome to iOS Brain”